These studies focus on: 1) the impact of adolescent age at first pregnancy on later pregnancy outcome; 2) the relation between interpregnancy interval and later pregnancy outcomes; 3) the risk of repeating poor pregnancy outcomes. The data sets are unique in that all pregnancies of women from Missouri and Utah are linked into sibships. These data allow the analyst to examine longitudinal pregnancy data. DESPR developed and cosponsored an international conference on nationally linked data sets. At this conference 6 abstracts were presented: the effect the accumulation of risks on pregnancy outcome, the effect of changing paternity on IUGR, recurrence risks for SIDS, recurrence risks for birth defects and a description of linkage methodologies in the area of maternally linked data sets. A special issue of the journal, Pediatric and Perinatal Epidemiology, is being prepared under the editorial direction of Dr. Herman and two colleagues from CDC & P, with the organizational and financial support of the Division of Epidemiology, Statistics and Prevention Research and its director, Dr. Berendes. Five pages from the two registries will be a part of the special issue.